Air gap arrester unit



May 14, 1957 D. L. BAXTER FAL AIR GAP ARRESTER UNIT Filed April 22, 1954 United States Patent() AIR GAP ARRESTER UNIT Donald L. Baxter, Elmhurst, and George C. Motsinger, Chicago, Ill., assignors to Reliable Electric Company, Chicago, Ill., a corporation of Illinois Application April 22, 1954, Serial No. 424,818

6 Claims. (Cl. 200-118) This invention relates to an air gap arrester unit, sometimes more broadly called a protector element, and more particularly to an air gap arrester unit for use in communication circuit protective devices such as indoor and outdoor drop wire protectors and cable terminals.

One object of the invention is to provide an air gap arrester unit which is detachably related to the protective device of which it forms a part. When necessary, the arrester unit is easily removed from the protective device and replaced with a new one.

Another object of the invention is to provide an air gap arrester unit which utilizes a more or less standard air gap arrester, the unit including improved means establishing electrical connection between the air gap arrester and the terminal elements of the unit.

Another object is to provide an air gap arrester unit which is easily `disassembled for purposes of inspection and which can be serviced by inserting a new arrester when the former one has broken down through normal operation.

Another object of the invention is to provide a resilient terminal contact member for an arrester unit of this character.

Still another object is to provide an arrester unit which includes a skirt element surrounding the terminal con.- tact member, the skirt element being effective to exclude dirt, moisture etc. from the terminal of the unit.

Other objects, advantages and details of the invention will be apparent as the description proceeds, reference being had to the accompanying drawings wherein one form of the invention is shown together with an exempiary protective device in which the arrester unit of the invention may be used. it is to be understood, however, that the description and drawings are illustrative only and that the scope of the invention is to be measured by the appended claims.

in the drawings:

Fig. l is a top plan view of an air gap arrester unit embodying the invention;

Fig. 2 is a sectional view on line 2 2 of Fig. l;

Figs. 3 and 4, respectively, are plan and elevational views of one element of the arrester unit;

Figs. 5 and 6, respectively, are plan and elevational views of a terminal contact member which may be used with the arrester unit, and

Figs. 7 and 8, respectively, are front and side elevational views of an exemplary protective device incorporating a pair of the arrester units of the invention.

Referring now to Figs. l and 2 of the drawings, an air gap arrester unit embodying the invention includes a sleeve 1? of electrical insulating material. Sleeve 1t) preferably is cylindrical in exterior shape for a purpose later to be mentioned, and it has a hollow interior 11.

VSleeve 16 is provided with a cap-securing means such as external threads 13 located at one end of the sleeve. These threads will be referred to later.

A conducting plug 1S is positioned at the other end of sleeve 10, the plug 15 preferably having the sleeve molded thereon as shown in Fig. 2. The inner end of plug 15 presents a dat surface to hollow interior 11 of the sleeve, while the outer plug end, in the form of the invention shown, extends somewhat beyond the end of the sleeve.

A more or less conventional carbon to carbon air gap arrester, preferably of the cylindrical type, is disposed within hollow interior 11 of sleeve 10. The illustrated air gap arrester comprises a carbon disk 17, a ceramic sleeve 18 surmounting disk 17 and a carbon. rod 19 carried by ceramic sleeve 1S with one end of rod 19 in spaced relation to disk 17. The other end of rod 19 extends exteriorally of sleeve 18 as shown in Fig. 2. A heat sensitive ycement 20 is used to secure rod 19 to ceramic sleeve 18, the relationship between rod 19 and sleeve 18 being such that an air gap 21 is provided between rod 19 and disk 17.

An air gap arrester of this character, when connected in a circuit, functions to discharge current across gap 21 and thence to an electrical ground when excessive voltage is applied during a short time interval. lf the excessive voltage persists, the heat generated by the resulting current is effective to soften heat sensitive cement 2i) whereby a force applied to rod 19 is effective to move rod 19 into contact with disk 17, thereby providing a closed shunt circuit.

As shown in Fig. 2, conducting disk 17 at one end of the arrester is in conducting relation with the flat inner surface of conducting plug 15. Thus a comparatively large Contact area is provided and the conducting path therebetween has desirably low resistance.

At the other end of the arrester a conducting member 23 has a comparatively large area in conducting relation with the extending end of rod 19. in the form of the invention shown, conducting member 23 takes the form of a cup-shaped spider member, the cup bottom of the member being in engagement with rod 19. Conducting member 23 has portions of comparatively large area which, as will be seen, provide a current carrying path. These portions, in the cup-shaped spider member shown, are resilient lingers which constitute the cup sides.

Details of the illustrated conducting member 23 are shown in Figs. 3 and 4. The cup bottom which engages rod 19 is designated 24 while the resilient fingers are designated 25.

A resilient conducting means such as a compression spring 27 extends between conducting member 23 and a fixed member, presently to be described, to exert a force on member 23 which is communicated to rod 19 of the arrester. This force is effective, when heat sensitive cement 26 is softened, to insure that rod 19 moves into direct contact with disk 17 to provide the aforesaid closed shunt circuit.

A conducting cap 3i) encloses conducting member 23 and spring 27, cap 3i) constituting the aforesaid fixed member against which spring 27 reacts. The exterior of a portion of cap 3i) preferably is hexagonal in shape for cooperation with wrenches which have become standardized in this field. Conducting member 23 has portions of comparatively large area which engage interior surfaces of cap 3d. ln the form of the invention shown, resilient lingers of the cup-shaped spider member are pressed against the interior surface of cap Si), thus affording a low resistance current path between conducting member 23 and cap 3) which, in the usual case, is connected to ground.

lt should be noted that compression spring 27, while extending between conductinf7 member 23 and cap 3d, is not relied on in this invention as the primary conducting path. Rather, the current travels between rod 19 and grounded cap 30 both through conducting member 23 and the low resistance path afforded by the large contact area of lingers 25 which are spring pressed against cap 3l) by the resilience of the lingers themselves and the conducting spring 27.

' C ap 3i) is suitably secured to sleeve 10, and in the formof the invention shown, cap 30 has a skirt 31 provided'with interior and exterior threads. The interior threads of skirt 31 engage cap-securing sleeve threads 13 as shown in Fig. 2 While the exterior skirt threads are available to secure the unit detachably in a protective device or other mount.

In most instances it is desirable to provide a resilient contact member as the non-ground terminal of the arrester unit. In the form of the invention shown, a resilient contact member 33 consists of a strip of conducting resilient material formed into a loop. Figs. and 6 illustrate the contact member in an intermediate stage of fabrication, the strip being designated by the numeral 35. Plug has an intermediate portion 36 of reduced cross section as shown in Fig. 2. The ends of strip 35 are centrally cut awa, as shown at 37-37 (Fig. 5), and they are Vreceived in overlapping relation within the plug portion of reduced cross section. This arrangement is Ysuch that the ends are retained in position, the strip 35 thus forming a resilient loop.

In use, the above described arrester unit has its cap V3ft) secured to a grounded mount, the opposite terminal, namely Contact member 33, being forced against a cooperating, iixed contact member connected to the protected circuit. The resilience of Contact member 33 is effective to insure a dependable connection with the cooperating, ixed contact member.

It is usually desirable to provide a means for excluding dirt, moisture etc. from the vicinity of contact member 33. In the illustrated form of the invention, a resilient skirt 3% of insulating material such as neoprene is mounted at the plugged end of sleeve lt), the skirt extending axially beyond contact member 33 so it may engage in a resilient manner the element which carries the aforesaid fixed Contact member.

Figs. 7 and 3 illustrate a protective device 4t) which incorporates a pair of air "ap arrester units embodying the invention. The numeral el designates a ground plate having circular openings therein, an arrester unit 42 being threaded into each opening. Ground plate 4i is mounted on and electrically connected to ground terminal Cap 3 of the arrester unit preferably has an enlargement d@ which engages plate al to limit the position of arrester unit with respect to the plate and increase the area of contact with the plate. Each arrester unit i2 cooperates with a terminal element ed to which,

for example, a drop wire of a telephone circuit is con-v nected. rierminal element carries a fixed contact member d5 which is engaged by resilient contact .member 33 of the arrester unit and scaled by skirt 3S.

It is apparent from Figs. 7 and S that arrester units i2 are easily detached from the protective device when it is necessary to inspect or replace them. In addition, a detached arrester unit 42 is easily disassembled by removing cap 33' which enables removal and inspection of the air gap arrester. if required, the latter can be replaced with a new arrester and the unit assembled for 'further use in protective device dit.

From the above description it is thought that the construction and advantages of the invention will be readily carent -ed in the art. Various to those siti changes in detail may be made without departing from the spirit or losing the advantages of the invention.

Having thus described our invention, what We claim as new and desire to secure by Letters Patent is:

l. An air gap arrester unit comprising an insulating sleeve having exterior threads at one end, a conducting plug closing the other end of said sleeve, an air gap arrester within said sleeve with one end of said arrester in conducting relation with said plug, a resilient, cupshaped spider member of conducting material in conducting relation with the other end of said air gap arrester at the threaded end of said sleeve, a compression spring Within said spider member and extending axially beyond the lsides thereof, and a conducting cap enclosing said spider member and bearing on said spring, said cap having a hexagonal shape exterior portion, the resilient sides of said spider member being in conducting engagement with said cap, said cap including a skirt having interior and exterior threads, the interior skirt threads engaging the exterior sleeve threads and the exterior skirt threads being adapted detachably to secure the unit in a conducting mount.

2. An air gap arrester unit comprising an insulating sleeve having cap-securing means at one end, a conducting plug at the other end of said sleeve, an air gap arrester Within said sleeve with one end of said arrester in conducting relation with said plug, a resilient, cup-shaped spider member of conducting material in conducting relation with the other end of said air gap arrester at said one sleeve end, a compression spring within said spider member with one spring end engaging said spider member and a conducting cap enclosing said spider member and bearing on the other spring end, the resilient lingers of said spider member being in conducting engagement with said cap, said cap engaging said cap-securing means of said sleeve.

3. An air gap arrester unit comprising an insulating sleeve having cap-securing means at one end, a conducting plug at the other end of said sleeve, an air gap arrester within said sleeve with one end of said arrester in conducting relation with said plug, a conducting 1nember having a comparatively large area in conducting relation with said air gap arrester, a conducting cap enclosing said conducting member and engaging said capsecuring means of said sleeve, said conducting member having portions of comparatively large area in spring pressed engagement with said cap, and resilient conducting means between said cap and said member exerting a force on said member which is communicated to said air gap arrester.

4. An air gap arrester unit comprising an insulating sleeve, a conducting plug at one end of said sleeve, an air gap arrester Within said sleeve with one end of said arrester in conducting relation with said plug, a conducting member having a comparatively large area in conducting relation with the other end of said arrester, a conducting cap enclosing said conducting member, said conducting member having portions of comparatively large area in spring pressed engagement with said cap, resilient means between said cap and said member exerting a force on said member which is communicated to said air gap arrester and a resilient contact member mounted on the outer end of said conducting plug.

5. The combination of claim 4 with the addition of a resilient, insulating skirt mounted at the plugged end of said sleeve and extending axially beyond said contact member.

6. An air gap arrester unit comprising an insulating sleeve, a conducting plug at one end of said sleeve, an air gap arrester Within said sleeve with one end of said arrester in conducting relation with said plug, a conducting member having a comparatively large area in conducting relation with the other end of said arrester, a conducting cap enclosing said conducting member, said conducting member having portions of comparatively large are-a in spring pressed engagement with said cap, resilient means between said cap and said member exerting a force on said member which is communicated to said air gap arrester, said conducting plug having an intermediate portion of reduced cross-section, and a strip of resilient conducting material formed into a loop with the two ends thereof being centrally cut away and received within the portion of reduced cross-,section to provide a resilient contact member.

References Cited in the file of this patent UNITED STATES PATENTS Ely Oct. 15, 1889 

